1. Field of the Invention
This invention relates to a high chemicals-resistant pipe coupling to be connected to a pipe for transferring a fluid.
2. Description of the Related Art
Conventionally, the coupling of pipes is provided with a spring for applying pressure to a valve. For example, a coil spring made of fluorine-contained polymers having a high resistivity for chemicals, a metal spring coated with such polymers, or a bellows-like spring is employed.
However, since the coil spring made of fluorine-contained polymers has a very small modulus of transverse elasticity, it cannot stand as great a load as a metal spring. The metal spring coated by fluorine-contained polymers cannot sufficiently be protected, because pin holes are easily formed in the coating. In a case where a bellows-like spring is used, since the fluid passage is narrowed when the spring is compressed, it is necessary to design the spring in consideration of an inner diameter of the bellows in its compressed state.